Start using Angular's conventional commits formatting

[DerekRoberts]

From https://github.com/angular/angular/blob/22b96b9/CONTRIBUTING.md#-commit-message-guidelines

<type>(<scope>): <subject>

Type:

• build: Changes that affect the build system or external dependencies (example scopes: gulp, broccoli, npm)
• ci: Changes to our CI configuration files and scripts (example scopes: Travis, Circle, BrowserStack, SauceLabs)
• docs: Documentation only changes
• feat: A new feature
• fix: A bug fix
• perf: A code change that improves performance
• refactor: A code change that neither fixes a bug nor adds a feature
• style: Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc)
• test: Adding missing tests or correcting existing tests

Scope (optional):

• The scope should be the name of the npm package affected (as perceived by the person reading the changelog generated from commit messages.

Subject:

• succinct description of the change
• use the imperative, present tense: "change" not "changed" nor "changes"
• don't capitalize the first letter
• no dot (.) at the end